The redmine plugin offer some features which are not documentedt and you can't guess.

RedmineMetrics
E.g How does the aggregate redmine ticket metrics feature works?
What does the target version settings do. Is it possible to autaomcatically set the target from jenkins variable to a already existing version in redmine for issues that has been sucessfully "build"? Can i use maven project version, so i only have to use same version numbers in redmine and maven artefacts? Does its create new version in redmine automcatically id they don't exits?

redmine site config
Why do i free text field for redmine.version property for site configuration. What shall i enter here and why..

redmine user auth

Are there any requuirements in redmine user password stroage (hashed, encrypted). Does it only authenticate users? Can i select groups from redmine if i use jenkins project base security?